You unlock super cars' by completing missions and you can increase your chance to win on the next mission. Besides that, you can drive freely on the map and you can try crazy things in the stunt arena. You can drive in the off-road areas freely by re-setting your car's wheel settings from the pause menu.
Move: "ARROW KEYS" Brake: "SPACE" Look Back: "B" Complete missions, buy new cars and participate in races.